WO2013079465A1

WO2013079465A1 - Method for the production of doubly spatially curved shells

Info

Publication number: WO2013079465A1
Application number: PCT/EP2012/073678
Authority: WO
Inventors: Johann Kollegger; Benjamin KROMOSER
Original assignee: Technische Universität Wien
Priority date: 2011-11-30
Filing date: 2012-11-27
Publication date: 2013-06-06
Also published as: AT511948B1; AT511948A4; EP2785933B1; EP2785933A1; ES2603190T3; PT2785933T

Abstract

The method for the production of a doubly spatially curved shell (1) comprises: placing a first sheet (5) and a second sheet (6) on a base surface (2), which sheets are tightly connected to one another at their edges; placing wedge-shaped pneumatic means (7) on the second sheet (6); inflating the wedge-shaped pneumatic means (7); producing shell segments (8) by laying a reinforcement and introducing a pourable, curing building material (9) between the wedge-shaped pneumatic means (7); arranging at least one flexible tension member (11) in the circumferential direction at the outer edge (4) of the base surface (2); mounting a load on the shell segments (8) along the outer edge (4); curving and raising the shell segments (8) by blowing in air between the first sheet (5) and the second sheet (6) with tensile loading of the tension member (11) in the circumferential direction; filling the joints (12) between the shell segments (8) with a curing casting material (13).

Description

Method for producing doubly spatially curved shells

The invention relates to a method for producing doubly spatially curved shells.

Shells are surface structures that can be used, for example, as a roof for exhibition halls or event halls.

Under two-dimensionally curved shells plate structures are understood, which are curved in two different spatial planes. Such doubly spatially curved shells can be used for example as a roof for exhibition halls or event halls.

Particularly suitable for the production of doubly spatially curved trays are materials which can be cast, such as e.g. Reinforced concrete, plastics, water or ice.

Shell structures are characterized by the fact that, with suitable form and storage, they carry off loads predominantly by membrane forces. This leads to an extremely low material utilization and low material consumption. However, the savings in material consumption are offset by increased labor costs for the production of spatially curved formwork. Executed shell structures, as described for example in "Spatial Roof Structures - Construction and Execution" by Hermann Rühle, Volume 1, VEB Verlag für Bauwesen, Berlin, 1969, p. 177, 248, 256 and "Heinz Isler - Schalen" by Ekkehard Ramm and Eberhard Schunk (ed.), Karl Krämer Verlag, Stuttgart, 1986, p. 51, 68, 70, 77 are described, generally have complicated, spatially curved formwork made of wood and / or steel.

In order to save the costs for the construction of spatially curved formwork, pneumatic formwork has become known. Shells in spherical or cylindrical shape and shells with more or less minor modifications of these basic shapes can be prepared in this way, see eg "domed construction with pneumatic formwork" by Franz Derflinger, in "Concrete and reinforced concrete", 1983, Issue 11, page 299 to 302. In order to change the shape of a pneumatic formwork, it is proposed in DE 35 00 153 to arrange on the surface of the pneumatic formwork radially extending cables which are biased against the pneumatic formwork. With the pneumatic formwork according to DE 35 00 153, the curvature of the formwork in the vicinity of the ropes is locally increased, which is favorable for the stability of the shell to be produced on this formwork.

Elaborate with pneumatic formworks is the production of the tires from blanks. The disadvantage is that the application of the building material of the shell in thin layers, e.g. by shotcrete, because the load capacity of the tires for evenly distributed loads is high, but local loads lead to large shifts.

The term "pneu" generally refers to an inflatable structure.

Since applying the shotcrete to the tire to produce a concrete shell or spraying water onto the tire to make an ice tray is a laborious manufacturing process, EP 1 706 553 has proposed mounting a plate of pourable material, such as e.g. Concrete or make water or ice on a flat work surface and then transform the plate into a shell by inflating a tire and tensing tendons. A disadvantage of this method is that a second soft material must be inserted in the plate, which plastically deforms during the forming process from the plate to the shell, but remains in the final shell. A further disadvantage is that the curvature of the shell to be produced by this method is limited, because the compressive stresses arising in the soft material during the forming process could lead to a stability failure of the areas with soft material. The areas of soft material are therefore limited to small dimensions.

In order to make it possible to produce a doubly curved shell from a flat initial shape, without leaving a second soft material in the final shell, it has been proposed in AT 506 902 to apply flat surface supporting elements to a tire, so that wedge-shaped interspaces between the planarized surface supporting elements remain. The shell is formed by the inflation of the tire and the tensioning of tension members. It has been found, see, for example, "Ice Domes - Development of Construction Methods" by Sonja Dallinger, Dissertation, Vienna University of Technology, 2011, that produced by this method shells are limited to small spans of about 10 m, because the tensile forces in the tire that equal to the Product of internal pressure and radius of curvature are, otherwise lead to a rupture of the joints of the tire.

The invention has for its object to provide a method for producing a doubly curved shell without the construction of a spatially curved formwork and the associated scaffold and without the complex manufacturing process of the injection of building material on a pneumatic formwork, which does not limit to small spans and bends and where no plastically deformed material remains in the final shell.

This object is achieved according fiction, by a method for producing a doubly spatially curved shell with the features of claim 1.

The method according to the invention comprises the following steps:

Laying a first film and a second film on a, preferably flat, base surface, wherein the films are sealed at their edges together; radial laying of wedge-shaped tires on the second film on a surface portion of the base surface, which corresponds approximately to the difference between the base surface and the surface of the shell;

Inflating the wedge-shaped tires;

Producing shell segments by laying a reinforcement and introducing a pourable and hardening building material on the base between the wedge-shaped tires;

Arranging at least one flexible tension member, which is displaceably formed with respect to the shell segments, in the circumferential direction on the outer edge of the base surface;

Applying a load on the shell segments along the outer edge of the base;

Warping and raising the shell segments by blowing air between the first and second foils under tensile load of the at least one tension member in the circumferential direction;

Fill the joints between the shell segments with a hardening potting material.

The base area is measured on a work surface, preferably a flat work surface, and dimensioned so that the base area is larger than the floor plan of Shell and at least the dimensions of the transmitted to the work surface surface of the shell.

After completion of the forming process, i. the warping and lifting of the shell segments, the individual shell segments are separated by joints. These are filled with a hardening potting material, whereby a high stability of the shell thus formed is ensured.

The shell segments are expediently formed of concrete, reinforced concrete, fiber concrete, textile-reinforced concrete, plastic or ice, since these materials ensure a high stability of the shell. Furthermore, tension members of tension wire strands, monolayers, stainless steel cables, stainless steel strands or fiber-reinforced plastic are expediently formed because they have the necessary tensile strength and flexibility.

Cement mortar, synthetic resin, plastic or water has proven itself as potting material.

According to a preferred variant, the two superimposed films are formed with a gas-permeable layer, in particular a non-woven fabric and / or textile fabric inserted between the films, wherein the superimposed films are sealed together at their edges and a Gaseinleitvorrichtung is provided on a film.

The films are expediently made of polyvinyl chloride or polyethylene in all conceivable variants.

A good fit to a curved shell through the shell segments is obtained if at least one shell segment is cut before the forming process, the cut is guided from the surface to near at least one reinforcement and is arranged approximately orthogonal to the reinforcement.

A preferred method is characterized in that the arrangement of shell-forming shell segments on the film is accomplished by pouring a castable material forming the shell segments, such as concrete, plastic or water, the base being provided with a peripheral edge shuttering for encasing the pourable material , In an expedient variant of the method according to the invention, a load is applied along the outer edge of the base surface, in that the thickness of the shell segments along the outer edge of the base surface is made larger than the thickness of the inner regions of the shell segments.

In a further variant of the method it is provided that, during the shaping process of the shell, the air pressure in the space between the first film and the second film is set differently from the air pressures in the wedge-shaped tire, adjusted independently of one another. If e.g. the air pressure between the films is set to be greater than the air pressure in the tires, this leads to a partial penetration of the film in the joints, which in turn may be advantageous for later removal of the tires from the joints, as will be explained below with reference to an embodiment.

Furthermore, it can be provided that the air pressure in the wedge-shaped tires is set differently in order to achieve a uniform closing of the joints during the shaping process. Preferably, the air pressures are adjusted so that the joints after completion of the molding process in plan view have an approximately rectangular shape.

In a preferred embodiment, a recess located in the center of the base is formed, and the shell segments are separated by the wedge-shaped tires laid therebetween, and the shell segments are joined together at the edge of the recess by a pull ring.

It has proven to be useful for carrying out the filling of the joints with potting material, if after the warping and lifting of the shell segments, the air pressure of the injected into the space between the first film and the second film air is maintained, the air is sucked out of the wedge-shaped tires and then filling the joints between the shell segments with a hardening potting material is performed.

In order to achieve a shell with high stability, it is expedient if a layer consisting of a building material is applied to the doubly curved shell after completion of the shaping process, which is shear-resistant connected to the doubly curved shell. In a further advantageous embodiment of the invention, the height of the wedge-shaped tires in the inflated state is at least equal to the thickness of the shell in a manufacturing process.

The invention is explained in more detail with reference to embodiments illustrated in the drawings.

Show it:

Figure 1 is a plan view of the work surface after laying the wedge-shaped tires and the production of the shell segments.

Fig. 2 is a section along the line II-II of Fig. 1;

FIG. 3 is a plan view corresponding to FIG. 1 on the shell after completion of the

Molding process;

Fig. 4 is a section along the line IV-IV of Fig. 3;

Fig. 5 is a section along the line V-V of Fig. 1;

FIG. 6 shows a section corresponding to FIG. 5 during the shaping process; FIG. Fig. 7 is a section along the line VII-VII of FIG. 3 after completion of

Molding process;

Fig. 8 is a section along the line VIII-VIII of Fig. 3;

9 shows a plan view analogous to FIG. 1 of a further embodiment;

FIG. 10 is a plan view corresponding to FIG. 9 of the shell after completion of the

Molding process;

Fig. 11 a of FIG. 10 corresponding plan view of the finished shell after

Applying an in-situ concrete layer;

Figure 12 is a section along the line XII-XII of Figure 11 through the shell.

Fig. 13 is a plan view corresponding to FIG. 10 with a representation of the

Tensile elements on the shell exerted forces;

FIG. 14 shows a section through the shell corresponding to FIG. 12, showing the forces exerted on the shell; FIG.

FIG. 15 shows a section along the line XV-XV of FIG. 9. FIG.

In the following, reference is made to FIGS. 1 and 2:

The first example illustrates the production of a bowl 1 of ice with the shape of a sphere section. The shell 1 could be used for example as Eisbar. As a first step, the outer edge 4 of a base 2 is measured and marked on a work surface 3.

As a second step, a first film 5 and a second film 6 are spread on the base 2. As the material for the films 5, 6, for example, polyvinyl chloride or polyethylene can be used in all variants. Between the films 5, 6 is advantageously a gas-permeable layer 15, for example a non-woven, arranged. The films 5, 6 are at this time, or later, peripherally sealed together.

As a third step, 6 wedge-shaped tires 7 are laid on the second film. The surface portion of the base 2, which is occupied by 7 Pneus corresponds approximately to the difference between the base 2 and the surface of the shell. 1

In the fourth step, the remaining part of the base 2 is filled in layers with water, which is allowed to freeze using a suitable, along the outer edge 4 attached Randabschalung and arranged in the middle of the base 2 pull ring 16 layers. Only after complete freezing of a layer of water, a further layer of water is sprayed. Upon reaching a certain thickness of ice, which corresponds to, for example, half the shell thickness, a reinforcement is laid. An advantageous type of reinforcement is e.g. by radially arranged tension wire strands 10, which are shown in Fig. 1, however, only in a shell segment 8, realized.

Along the outer edge 4, a relative to the building material 9, here ice, displaceable tension member 11 is arranged. Such a tension member could for example consist of a greased and arranged in a polyethylene cladding tension wire strand. The ice thickness along the outer edge 4 is increased as shown in FIG. 2, so as to provide an additional load.

In the fifth step, the shell segments 8 are formed by blowing in air between the first film 5 and the second film 6 and by tensile loading of the tension member 11.

As shown in FIG. 3 and FIG. 4, the diameter of the shell 1 after the completion of the molding process is smaller than the diameter of the planar initial shape.

The air pressure in the wedge-shaped tire 7 can be changed during the production of the ice sheets, so that a section through the tire 7 according to FIG. 5 has a rectangular shape as possible. A tire is characterized by a compared to the Tensile rigidity negligible bending stiffness. Therefore, a cross section through the tire 7 as shown in Fig. 7 will have bulges.

The tire is attached either to the second film 6 or to the shell segments 8 to prevent the tires 7 from sliding out during the molding process. In Fig. 5 loop-shaped anchors 17 are shown made of plastic, with which the tire 7 is attached to the shell segments 8.

During the molding process, the distance between the shell segments 8 becomes smaller and the joints 12 become smaller. FIG. 6 shows that the gap 12 has been reduced in comparison to FIG. 5. The tire 7 is bulged upwards at the top. The air pressures in the space between the films 5, 6 and in the wedge-shaped tires 7 can be adjusted independently. 6 shows a situation in which the air pressure between the films 5, 6 is greater than the air pressure in the tire 7, which leads to a partial penetration of the film 6 into the joint 12. The air pressure in the tires 7 can either be the same or be changed for individual tires 7 in order to achieve a uniform closing of the joints 12 during the shaping process.

After completion of the shaping process, the air can be sucked out of the tires 7. FIG. 7 shows how the tire 7 can be pulled out of the joints 12 by suction, so that it comes to lie under the shell segments 8. Subsequently, the gap 12 can be filled with a potting material 13. The lower gap of the joint 12 is sealed by the tire 7 and by maintaining an air pressure in the space between the films 5, 6, so that the potting material 13 does not escape from the joint.

The geometric relationships during the molding process for producing the shell 1 with the shape of a spherical segment are shown in FIG. 8.

The curvature k of the shell 1 or of the shell segment 8 corresponds to the reciprocal of the radius R. The curvature k is also equal to the sum of the elongation of the reinforcement e _s and the compression e _{c of} the building material 9 at the lower edge of the shell segment 8 divided by the length d, which corresponds to the distance between the reinforcement of tension wire strands 10 and the lower edge of the shell segment 8. The reinforcement must not be stressed during the forming process above the yield point, which marks the end of the linear relationship between stresses and distortions, because otherwise there will be no uniform curvatures in the shell segments 8, but locally large cracks. Therefore, it is favorable to have a reinforcement with high strength, such as Tension wire strands 10 with a flow limit of about 1600 N / mm to use to achieve high strains and thus large curvatures. A further increase in the curvature is achieved by a reduction of the distance d, which means that the reinforcement is not arranged on the drawn edge of the shell segment 8, but, for example, in the middle in the shell segment 8. It is advantageous to provide the shell segments 8 with cuts 18 extending from the top to near the reinforcement to provide controlled cracking.

A further exemplary embodiment is explained with reference to FIGS. 9 to 14 for the production of a doubly spatially curved shell 1, in which concrete is used as building material 9. The shell 1 could be used as wild overpass over railway tracks.

According to the example explained in FIGS. 1 to 8, the base area 2 is first measured in accordance with FIG. 9. Then, a first film 5, a second film 6 and wedge-shaped tires 7 are laid, and a suitable Randabschalung is prepared. The base 2 consists of two semicircles and a rectangle arranged therebetween. Wedge-shaped tires 7 are arranged only in the semi-circular portions of the base 2. The tires 7 in this example are intended to be connected to the second film 6, e.g. be connected by a bond.

Then a rebar of concrete steel is laid, the tires 7 are inflated and poured concrete as building material 9.

The shaping process, which is carried out after the hardening of the concrete, results according to FIG. 10 in a reduction of the circumference of the shell 1 in comparison to the length of the outer edge 4 of the base 2.

While maintaining the air pressure between the foils 5, 6, a reinforcement can then be laid on a part of the surface of the shell 1 according to FIGS. 11 and 12 and an in-situ concrete layer 19 applied. After hardening the in-situ concrete layer 19, the edge regions of the shell 1, which are not covered with an in-situ concrete layer 19, can be broken off in order to create openings for the tracks under the shell 1.

Fig. 13 shows the forces exerted on the shell 1 by the tension members 11 and 11 'during the molding process. The laid along the outer edge 4 tension member 11 exercises in the areas where it along the outer edge. 4 was displaced circular, deflection forces u on the shell edge. The currently laid tension members 11 'exert anchoring forces F on the shell edge.

14 shows in a section the effect of the deflection forces u of the tension member 11 and of the air pressure p between the foils 5, 6 on the shell 1. At any time during the shaping process, an equilibrium state between the own weight of the shell and the anchoring forces F, the deflecting u. and the air pressure p.

FIG. 15 shows a section corresponding in principle to FIG. 5, however, with a modified embodiment of the wedge-shaped tires 7. The wedge-shaped tires 7 each here comprise two planar films which are welded together along their edges.

In the examples, the production of bowls with a circular and elliptical-like outline has been described. With the method according to the Invention, however, the production of doubly spatially curved shells of any shape over any plans is possible.

LIST OF REFERENCE NUMBERS

1 bowl

2 base area

3 work surface

4 outer edge

5 first slide

6 second slide

7 wedge-shaped tires

8 shell segment

9 building material

10 tension wire strands

11 tension member

12 fugue

13 potting material

14 recess

15 gas-permeable layer

16 pull ring

17 anchoring

18 incision

19 in situ concrete layer

Claims

claims

1. A method for producing a doubly spatially curved shell (1), characterized by:

• applying a first film (5) and a second film (6) on a, preferably flat, base surface (2), wherein the films (5, 6) are sealed at their edges;

Radially placing wedge-shaped tires (7) on the second film (6) on a surface portion of the base surface (2) which corresponds approximately to the difference between the base surface (2) and the surface of the shell (1);

• inflating the wedge-shaped pneus (7);

• producing shell segments (8) by laying a reinforcement and introducing a pourable and hardening building material (9) on the base (2) between the wedge-shaped tires (7);

• Arranging at least one flexible tension member (11) which is designed to be displaceable relative to the shell segments (8), in circumferential direction on the outer edge (4) of the base (2);

• attaching a load on the shell segments (8) along the outer edge (4) of the base (2);

• bending and raising the shell segments (8) by blowing air between the first film (5) and the second film (6) under tensile load of the at least one tension member (11) in the circumferential direction;

• Filling the joints (12) between the shell segments (8) with a hardening potting material (13).

2. The method according to claim 1, characterized in that not the entire base surface (2) with wedge-shaped Pneus (7) and a hardening building material (9) is occupied, whereby recesses (14) arise in the shell (1) one or form a plurality of predetermined recesses.

3. The method according to claim 1 or 2, characterized in that between the first film (5) and the second film (6) a gas-permeable layer (15), preferably formed from a non-woven and / or textile fabric, is laid.

4. The method according to any one of claims 1 to 3, characterized in that the step of attaching a load along the outer edge (4) of Base (2) by means of an increase in the thickness of the shell segments (8) along the outer edge (4) of the base (2) is performed.

5. The method according to any one of claims 1 to 4, characterized in that during the molding process of the shell (1) the air pressure in the space between the first film (5) and second film (6) different from the air pressure or the air pressure in the wedge-shaped Pneus (7) is set.

6. The method according to any one of claims 1 to 5, characterized in that the

Air pressures in the wedge-shaped tires (7) are set differently.

7. The method according to any one of claims 1 to 6, characterized in that in the middle of the base surface (2) lying recess (14) is formed, that the shell segments (8) are separated by the wedge-shaped tires (7) laid therebetween , and in that the shell segments (8) are connected together at the edge of the recess (14) by a pull ring (16).

8. The method according to any one of claims 1 to 7, characterized in that after the warping and lifting of the shell segments (8) of the air pressure in the space between the first film (5) and second film (6) is maintained air, the Air is sucked out of the wedge-shaped tires (7) and then the filling of the joints (12) between the shell segments (8) with a hardening potting material (13) is performed.

9. The method according to any one of claims 1 to 8, characterized in that on the doubly curved shell (1) after completion of the shaping process, a layer consisting of a building material (9) is applied, the shear with the doubly curved shell (1) becomes.

10. The method according to any one of claims 1 to 9, characterized in that the

Shell segments are made of concrete, reinforced concrete, fiber concrete, textile reinforced concrete, plastic or ice.

11. The method according to any one of claims 1 to 10, characterized in that the

Tension members are formed from tension wire strands, monostrands, stainless steel cables, stainless steel strands or from fiber-reinforced plastic.

12. The method according to any one of claims 1 to 11, characterized in that as

Grout cement mortar, synthetic resin, plastic or water is used.

13. The method according to any one of claims 1 to 12, characterized in that the height of the wedge-shaped Pneus (7) in the inflated state is at least equal to the thickness of the shell (1).

14. Double spatially curved shell (1), produced by a method according to one or more of claims 1 to 13, characterized in that the shell (1) alternately from at least one building material (9) with a reinforcement (10) and at least one with a curing potting material (13) filled joint (12) is composed.